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Sub woofer story.

Our sub woofer has been designed to perform for both home theatre and music applications.
It operates as a BANDPASS system and will only reproduce a very narrow range of frequencies, thus not imposing on the main audio channels.
It is in the sense a true Sub woofer.
It has a useful lower frequency response below 20Hz, whilst its upper frequency limit is capped at 60Hz.
Bandpass enclosures are essentially 2 chambers (boxes) back to back, with the driver (woofer) mounted between the 2 boxes.
The rear chamber operates in sealed or closed box mode, and when combined with driver specifications, governs the lower frequency response.
The front chamber is a vented or ported enclosure.  This chamber/driver relationship governs the bandwidth or frequency response of the system.
Careful design of this type of system is imperative, as the driver has to match not one but two enclosures.
The driver also has to have the ability to cope with the demands of low frequencies.
As the frequency response drops, woofer cone excursion dramatically increases.
It is pointless designing a system that is capable of getting down to subsonic frequencies if the woofer does not have the cone excursion to cope.
The driver used in our system has a cone excursion of 45mm., which will cope with very large low frequency demands.
The audio output is directed outside via the vent, which is tuned to a certain frequency. (Like a single tube of a pipe organ)
The vent/enclosure relationship becomes the natural resonant frequency of the system, and will only allow frequencies of around 16Hz either side of resonance to be passed, giving a bandwidth of approximately 40Hz.
Because of the systems narrow bandwidth, no crossovers are required adding coloration and distortion.
Having the sub woofer’s upper frequency response limited to 60Hz., prevents it from interfering with the “sound” coming from the main left/right front loudspeakers.
This I believe makes for a great compromise for all types of software material.
It is particular noticeable with many commercially made home theatre sub woofers being used in music applications, giving a very hard and boxy sound…It is particularly evident if the operating frequency response is higher than 70Hz., which may sound great on explosions etc., but poor on music discs.
These systems audio quality greatly improves, once the sub woofer is turned off.
The twin chambers used in the construction are extensively braced, with the vent being an integral part of the front enclosure and the main internal driver baffle plate, making it very ridged and strong.
Dimensions   55cm x 55cm x 40cm high.
35 mm timber top. (Various timber types)
Twin chamber Band pass System.
200 watt RMS fully adjustable internal amplifier.
Lower frequency response: below 17Hz.
Upper frequency response: adjustable to 60Hz.
Bandwidth approximately 40Hz.
Maximum output 116dB (Thermal Limit)
Sensitivity 92dB.
*specifications subject to change without notice